Random Misfire at low RPM
07-11-2007, 10:27 PM
#22
my car is doin the same thing right now and from what all i have read on this site goin crazy is that it has to be a coil pack .. i did wires and plugs but still nothing. so tomarrow im goin to buy a coilpack and start guessin just doin each one and hopefully thats it.i have no idea how to check each one..
07-12-2007, 12:23 AM
#23
Coil packs normally just die suddenly, not crap out slowly. They also rarely fail. Ignition system is not a weak point of these cars. Dirty injectors are FAR more common. Is it running rich or lean, especially under load? Your fuel filter could have hurt the pump and be making it weak. This CAN cause misfires or pinging under load, sometimes stumbling at high RPM that won't throw codes. Check fuel pressure to rule it out.
07-12-2007, 10:21 AM
#25
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I changed the fuel filter the day I bought it. It looked to have the original GM filter on there at 70,000 miles. What is the easiest way to check the fuel pressure?
Other than that I'm thinking of running with as is, with the catch can for a couple hundred miles and then seafoaming again and checking plugs.
Other than that I'm thinking of running with as is, with the catch can for a couple hundred miles and then seafoaming again and checking plugs.
07-13-2007, 09:16 PM
#27
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after 100 miles i have about 3 tablespoons of oil in the catch can. I reset the computer and let the engine relearn everything today. It feels better. Better throttle response and better high end. I didn't tell the wife I did anything to it and let her drive and she thought I had changed something because of how much better it accelerates.
I still get the shaking if I hold the rpm's at around 1200.
The hunt continues.
I still get the shaking if I hold the rpm's at around 1200.
The hunt continues.
08-02-2007, 10:32 AM
#30
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Mine always had a little bit of random misfire ever since I started
scanning. At idle it doesn't bother anything. If you got the idle
dead smooth maybe it would go away but there is a lot of crap
goes on, adaptive spark, proportional fuel swinging, that drives
the motor right to (or past) the edge of misfiring. Mine always
had a "facial tic" at idle, every couple of seconds the motor
would jerk once.
If you eliminate all that fooling around you might be able to
smooth it out but say goodbye to closed loop idle and hello
to a whole lot of fiddling.
Where misfires matter, is at cruise with your converter locked
(you wish). Elsewhere it's just information without effect until
something goes pretty far wrong.
scanning. At idle it doesn't bother anything. If you got the idle
dead smooth maybe it would go away but there is a lot of crap
goes on, adaptive spark, proportional fuel swinging, that drives
the motor right to (or past) the edge of misfiring. Mine always
had a "facial tic" at idle, every couple of seconds the motor
would jerk once.
If you eliminate all that fooling around you might be able to
smooth it out but say goodbye to closed loop idle and hello
to a whole lot of fiddling.
Where misfires matter, is at cruise with your converter locked
(you wish). Elsewhere it's just information without effect until
something goes pretty far wrong.
08-03-2007, 11:04 AM
#31
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Yeah, I'm having a similar issue with mine, except mine occurs while cruising and the converter is locked up. I just started my search and ran across this thread. Any ideas there?
08-03-2007, 01:09 PM
#32
This is probably no help to you since you've already seafoamed but I'll post anyway.
Ever since I bought my car it had what felt like a slight miss at idle pretty much what you're experiencing. I didn't worry about it really since V8's never seem to idle quite as smooth as a 4cyl. Anyway, I ran a can of BG44k through the tank and it definitely idles much more smoothly now. Do the normal maintenance stuff but don't drive yourself crazy over it, because whatever it is, it sounds pretty minor.
Ever since I bought my car it had what felt like a slight miss at idle pretty much what you're experiencing. I didn't worry about it really since V8's never seem to idle quite as smooth as a 4cyl. Anyway, I ran a can of BG44k through the tank and it definitely idles much more smoothly now. Do the normal maintenance stuff but don't drive yourself crazy over it, because whatever it is, it sounds pretty minor.
08-26-2007, 12:27 PM
#34
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I was wondering if you had any luck with the o2 sensors I have an o2 Z28 with the same problem the check engine light is not on but if you hook up the scanner you get a multiple cylinder missfire p0300 I believe was the code it misses very bad at idle but if you rev it over 1200 rpms it runs great I have changed plugs wires you name it just recently changed the crank sensor I was told could be the problem but it did not help on the scanner the 02 sensors appear to be functioning properly any help would be great
09-05-2007, 02:36 PM
#35
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Originally Posted by camaro3773
I was wondering if you had any luck with the o2 sensors I have an o2 Z28 with the same problem the check engine light is not on but if you hook up the scanner you get a multiple cylinder missfire p0300 I believe was the code it misses very bad at idle but if you rev it over 1200 rpms it runs great I have changed plugs wires you name it just recently changed the crank sensor I was told could be the problem but it did not help on the scanner the 02 sensors appear to be functioning properly any help would be great
does anyone have any ideas before I start changing o2 sensors
09-05-2007, 05:47 PM
#36
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I haven't been able to track it down anymore. Headers and new o2's have been put on hold for a while. I noticed after the catch can mod that the inside of the tips on my exhaust are alot cleaner. I would have to clean them every week, now I only do it once a month and didn't really need it. I'm going to seafoam again in a week, I'll post results.
09-13-2007, 03:32 PM
#37
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Originally Posted by camaro3773
does anyone have any ideas before I start changing o2 sensors
09-13-2007, 05:09 PM
#38
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Originally Posted by camaro3773
Well I changed o2 sensors and still has a miss on all cylinders when you hook up a scanner all of the o2 sensors at idle are jumping from 50 to 800 volts should they be fluctuating this much could bad convertors cause such a problem
Someone correct me if I am wrong on this...
04-04-2008, 05:58 PM
#39
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UPDATE: Long time coming but I replaced the 2 front o2 sensors (thanks 89formulaws6). Cranked the car up and no more shaking. Taking it to get scanned tomorrow after alignment.
One o2 sensor looked "whiter" than the other is that normal?
One o2 sensor looked "whiter" than the other is that normal?
04-05-2008, 05:09 PM
#40
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No misfires on the scanner at all. Car idles perfectly now. Runs alot smoother, I almost thought it died at one point in time because of how smooth it is.